A Republican candidate under fire for saying women's bodies can prevent pregnancy in rape cases has lashed out at party bosses who want him to quit.

Congressman Todd Akin said it was not right for the party establishment to over-ride Missouri voters who had picked him to run for the Senate.

In a new fundraising appeal, Mr Akin claims "the liberal elite" are trying to take down a "pro-life conservative".

But he has agreed not to attend next week's party convention.

Correspondents say the furore over Mr Akin's rape remarks could derail the Republican campaign to win control of the US Senate in November's elections.

Prominent Republicans have lined up to call on him to quit, while the party and its supporters have pulled the plug on millions of dollars of funding.

'Medically wrong'

But Mr Akin struck his most defiant tone yet on ABC's Good Morning America programme on Wednesday: "The people of Missouri chose me, and I don't believe it's right for party bosses to decide to over-ride those voters.

It seems strange that a 21st Century politician is willing to legislate on the grounds of old wives' tales

By Mark MardellNorth America editor

"It makes me uncomfortable to think that the party bosses are going to dictate who runs, as opposed to the election process."

He also continued to back-pedal from his comments last Sunday about "legitimate rape", accepting that the views he expressed were "medically wrong".

Although Tuesday was the final day for Mr Akin to withdraw from the race without a court order, he did not categorically rule out stepping aside at a later date.

"I'm never going to say everything that could possibly happen," he told ABC. "I don't know the future."

Mr Akin also confirmed that Republican vice-presidential candidate Paul Ryan had urged him to end his campaign.

'Forcible rape'

While Republican presidential candidate Mitt Romney has said he believes abortion should be allowed for rape victims, his running mate has previously taken a harder line.

Mr Ryan, a Wisconsin congressman, co-sponsored along with Mr Akin and other lawmakers a controversial bill that would ban federal funding for abortion with a rape-exception only in cases of "forcible rape".

Media captionMissouri resident: "He just shot himself in the foot''

On Wednesday, the Republican running mate was asked in an interview to define forcible rape.

Democrats are trying to portray Mr Akin's comments on rape as symptomatic of a negative attitude towards women across the Republican party.

There has been renewed focus on a Republican convention platform, which resurfaces every election year, for a constitutional ban on abortion with no exceptions for rape or incest. It will be voted on next Monday at the party gala in Tampa, Florida.

In an appeal for $5 campaign donations on Wednesday, Mr Akin appeared to pitch to Christian evangelicals, anti-abortion activists and anti-establishment Republicans.

He accused Republicans of trying to "duck and run for cover" in the face of adversity over the row.